Method for managing power supply to a cellular radiotelephone station

ABSTRACT

The process for controlling the power supply ( 16 ) of a telephone ( 1 ) of a cellular radiotelephone network ( 2 ), of which the transmission power ( 13 ) is controlled ( 14 ) by the network ( 2 ) according to a power class indicated by the telephone ( 1 ), consists of 
     determining the charge level of the power supply ( 16 ), 
     deducing the maximum transmission power able to be reached, according to the charge level, 
     comparing the maximum transmission power and the transmission power controlled ( 14 ) by the network ( 2 ), and 
     downgrading the mobile telephone ( 1 ) if the former is lower than the latter ( 14 ).

In a cellular radiotelephone network, such as the GSM network, themobile telephones transmit to the base stations at a power level whichdepends on the construction characteristics of each type of telephoneand which are defined by a power class.

This class is stored in the telephone and, when it is energised, itannounces itself to the network by automatically transmitting this classand various data indicating its characteristics and its functions. Whencommunication is established, the network controls the level oftransmission of the telephone according to this class, ie. in the caseof low reception at the base station linked to the telephone, thenetwork will attempt to remotely control an increase in the transmissionlevel of the telephone only if the maximum transmission level associatedwith its class has not already been reached. Otherwise the network willsimply attempt to correct the errors in reception.

As long as the maximum level has not been reached the network remotelycontrols the level of transmission of the telephone so that this will bejust sufficient to avoid errors, this avoids wasting the telephone'spower and is thus advantageous to its autonomy.

The radio transmission represents a large part of the telephone'sconsumption, it having very limited autonomy in the power supply,batteries or cells, storing electrical power. In the case of severedischarging, the power supply is incapable of supplying the desiredcurrent and must be changed or recharged.

The present invention aims to prolong the “lifespan” of such a powersupply, ie. to increase the quantity of useful power that it is possibleto extract therefrom between two recharges, if this is the case.

To this end, the invention relates to a process for controlling thepower supply of a telephone of a cellular radiotelephone network, ofwhich the transmission power is controlled by the network according to anominal power class indicted by the telephone, characterised in that

the charge level of the power supply is determined,

the maximum transmission power able to be reached is deduced from thecharge level,

the maximum transmission power and the transmission power controlled bythe network are compared, and

the mobile telephone is downgraded if the former is lower than thelatter.

Thus, when the power supply becomes incapable of providing the desiredpower it is possible to proceed with the extraction of power therefromin a downgraded mode of operation which requires less power.

The telephone is advantageously downgraded into a fictitious class oftransmission power lower than that of the nominal class.

It is thus possible to return to standard operation with automatic powercontrol but in a lower range of transmission power levels.

In this case any connection between the telephone and the network ispreferably cut in order then to reestablish such a connection and totransmit the indication relative to the fictitious class.

The switching between classes thus does not risk disrupting the networksince this network cannot establish a logic link between the telephonewhich has “disappeared” and the same telephone reappearing withimmediately reduced power.

The invention will be better understood with the aid of the followingdescription of a preferred embodiment of the process of the inventionand with reference to the single figure which schematically shows aradiotelephone for implementation of the process of the invention and aradio base station.

The telephone 1 of the cellular radiotelephone network can be connectedto a base station 2 of the network, in this case the GSM. The telephone1 comprises a standard assembly 11 of voice circuits: analogue interfacecircuits, loudspeaker, microphone, the latter controlling, via anencoder 12, an antenna amplifier 13 charged by a transmission-receptionantenna 10.

In reception, the antenna 10 controls a reception amplifier 14controlling the loudspeaker of the circuit 11 via a decoder 15.

The group of circuits illustrated is supplied by a power source 16storing electrical power, in this case a group of cells. The powersupply 16 thus supplies, in particular, the amplifier 13 havingadjustable transmission power controlled by a circuit 18 for controllinggain, or power level, which is itself controlled by the output of thedecoder 15 which, amongst other things, receives, to this end, remotecommands from the station 2.

The charge level of the power supply 16 is monitored by a sensor 17connected at the output to the circuit 18. The sensor 17 in this casemeasures the voltage of the power supply 16; in other examples anammeter could be provided or even a temperature sensor which is alreadyprovided for safety reasons.

Furthermore, a microprocessor 20, controlling all the circuits, isconnected to a read-only memory 21, containing data for identifying theterminal 1, which can be read by the encoder 12 via the microprocessor20.

The operation of the telephone 1 is as follows, with respect to thecontrol of the power supply 16.

When the telephone 1 is active and receives remote commands for controlof the level of transmission (13), the charge level of the power supply16 is determined, the maximum transmission power able to be reached isdeduced from the charge level, the maximum transmission power and thetransmission power (14) controlled by the network 2 are compared, andthe mobile telephone 1 is downgraded if the former is lower than thelatter (14).

The downgrading can consist of adopting another predetermined class,passing from 2 watts to 0.8 watts, for example, or simply of notreaching the desired transmission level by refusing to carry out theremote commands without the actual transmission level or the maximumlevel necessarily corresponding to a predetermined class. In this lattercase, transmission will preferably be carried out at the maximumpossible level taking account of the charge level of the power supply inorder to best approach the level expected by the station 2.

On the other hand, in the case where there is a transition to a specificlower class, the level required by the station 2 will be reduced afterthe telephone 1 transmits the new class to it, so that the remotecommands (for increase) of the level of power which it transmits will beexecuted again since a safety margin will have been re-established bythe lowering of the class. The process of class reduction can continueto other, lower classes. During the downgrading the network can, forexample, allocate the telephone 1 to another station closer to it thanthe station 2, even if this other station is more busy, in order toimprove the quality of the connections.

The process of controlling the power supply 16 will be explained in moredetail.

When the telephone 1 is energised, it announces itself to the station 2by transmitting its identification data contained in the memory 21. Thenetwork 2 thus knows the class of the telephone 1, ie. the maximum powerwhich it can request it to transmit. When the telephone 1 is moving, thenetwork 2 can thus remotely control the circuit 18 to adjust thetransmission power (13) to a level sufficient for good reception at thestation 2 without, however, wasting power by using an excessive level oftransmission.

If the station 2 only receives too low a level from the telephone 1, ittransmits a remote command to raise the transmission level (13) again.If, in the case of interest here, the power supply 16 has a charge levelinsufficient to provide the transmission power corresponding to thedesired level, the telephone 1 is then downgraded.

In this case the charge level is estimated according to the voltage ofthe power supply 16 which falls as it is discharged. The circuit 17measures, in particular, the at-rest voltage, with low discharge, in theabsence of transmission, which provides a first estimation of the chargelevel, and also measures the voltage at high output, duringtransmission, which provides a second indication of the charge level, byestimating, in fact, the internal resistance of the power supply 16since the current absorbed normally by the antenna 10 and the variouscircuits is known.

The circuit 18 then exploits these measurements to accept or reject aremote command aiming to increase the transmission level. In order tomodify the class announced to the network 2, the circuit 18 controls themicroprocessor 20 which then transmits an indication of a fictitiousclass (or of maximum power) lower than that in the memory 21. Provisioncan be made for the power supply of the telephone 1 to be cut, or forthe microprocessor 20 to control such a cut by a switch, not shown,telephone 1 which thus “disappears” from the network 2 in order then toreappear by reestablishment of its power supply, announcing thefictitious class thereof, in this case 0.8 watts, which avoids the riskof disrupting the network 2 by a transition of classes which it woulddetect if the connection thereto were maintained. In a variation, itwill suffice simply to cut and then to reestablish the connectionbetween the telephone 1 and the network 2.

If the discharge of the power supply 16 is too great, it is alsopossible to prevent any transmission of voice signals and to maintainonly the reception of messages from the network 2, for example shortwritten messages, ie. any outgoing call is prevented while thetransmissions of signals to control the incoming calls is permitted. Thetelephone 1 thus operates as a receiver of messages (pager), its userbeing informed of the identity of the correspondents who are calling it.

The telephone number identifying the calling telephone is then detectedin the messages received, formed from the message sent by the callingtelephone and signals identifying it, and it is applied to user-machineinterface means such as a display or voice synthesiser.

In order to economise further on energy it is even possible to preventany transmission, even of signals for controlling incoming calls. Thearrival of a call is simply detected and signalled by a means of thetype indicated above, for example, a buzzer.

In practice the control circuit 18 can exist only functionally, ie. canbe integrated into the microprocessor 20 or into an equivalent centralunit controlling the adjustment of the transmitter 13 in a time-sharingmanner.

What is claimed is:
 1. Process for controlling the power supply (16) ofa mobile telephone (1) of a cellular radiotelephone network (2), ofwhich the transmission power (13) is controlled (14) by the network (2)according to a power class indicated by the telephone (1), the processbeing characterised in that the charge level of the power supply (16) isdetermined, the maximum transmission power able to be reached is deducedfrom the charge level, the maximum transmission power and thetransmission power controlled (14) by the network (2) are compared, andthe mobile telephone (1) is downgraded if the former is lower than thelatter (14).
 2. Process according to claim 1, wherein in order to bedowngraded, the telephone (1) rejects the power command of the network.3. Process according to claim 1, wherein the telephone (1) is downgradedinto a fictitious class of transmission power lower than that of thenominal class.
 4. Process according to claim 3, wherein any connectionbetween the telephone (1) and the network (2) is cut in order then toreestablish such a connection and transmit the indication relating tothe fictitious class.
 5. Process according to claim 4, wherein theconnection is cut by cutting the power supply (16) of the telephone (1).6. Process according to claim 1, wherein the maximum transmission poweris estimated according to the current output by the power supply (16).7. Process according to claim 2, wherein the maximum transmission poweris estimated according to the current output by the power supply (16).8. Processing according to 3, wherein the maximum transmission power isestimated according to the current output by the power supply (16). 9.Process according to claim 4, wherein the maximum transmission power isestimated according to the current output by the power supply (16). 10.Process according to claim 5 wherein the maximum transmission power isestimated according to the current output by the power supply (16).